Manipulating Methanethiol Formation and Degradation Rates for Odor Emission Control

Abstract. Odor emission from agricultural facilities poses serious nuisance to surrounding communities. The extremely volatile methanethiol (MT) formed in the course of amino acid fermentation has been identified as a major odorous compound generated from many agricultural facilities and waste management practices such as livestock housing, vegetable storage, solids waste composting, anaerobic digestion and land application of biosolids etc. Methanogens are able to swiftly assimilate and convert MT, and thus can be taken advantage as a potential biological tool for odor mitigation. It is our hypothesis that the emission of MT, as an intermediate compound, can be effectively controlled by manipulating the growth rate difference between its producers (methionine fermenters) and MT utilizers (methanogens). To very this hypothesis in practice, we operated six floor-scale anaerobic digesters in chemostat mode with six HRTs (15, 20, 25, 30, 40, 50 days). By virtue of the growth kinetics disparity, different concentrations of MT producers and utilizers were successfully enriched in these chemostats at steady state, indicated by MT formation rate and methane generation rate respectively. The corresponding MT contents measured in biogas emitted from these chemostats turned out to be in line with the prediction of the mathematical model that describe the dynamic relationship between MT formation and utilization with considerations of product inhibition and substrate limitation. Further experiment was also carried out to cross-verify the MT formation kinetics and pathway by directly controlling the growth rates of MT producers and utilizers with chemical inhibitors. Based on the mechanism verified in this study, chemical and biological measures were proposed for engineers to adopt for odor mitigation and control in agricultural practice.